HTML5 Web APIs

Exercise: WebSockets

The backend chat service provides a WebSocket API at the URL wss://chat.distsys.ch. After having connected, a client receives event messages when a user's state changes or a message is sent.

• Use the JavaScript file store.js to store the fetched users and messages locally.
• Implement subscribeUsers and subscribeMessages functions that connect to the corresponding WebSocket channels and update the local users and messages when event messages are received.
• Invoke the two subscription functions after having fetched the existing users and messages.
• Remove the polling mechanisms in the users and messages components.